Seven members of the Katuci family sat silently in their living room, hands on knees, as rain tapped at the window. They had been asked if they hosted one of the most macabre war crimes of the 1999 Kosovo war. And they did not want to talk.

It was to their country house in northern Albania's mountain region that Kosovan Albanian guerrillas are believed to have brought hundreds of captive Serbian soldiers to cull their organs in the aftermath of Nato's bombing.

"I did not do it," said Mercim Katuci, the 50-year-old head of the family, breaking the silence with a shot of liquor. "That is why I am angry. Shame has been brought on us. People in the village tell us: 'You killed the Serbs. You are evil people.' We are poor people - how could we kill hundreds of soldiers in this house?"

The spotlight will soon fall on the house again when a fleet of 4x4 vehicles brings Dick Marty - a special investigator mandated by the Council of Europe to re-examine the case - and his team up a crumbling dirt track, seven miles south of the town of Burrel.

There have been calls for an investigation into the Burrel "house clinic" since April, when the ex-chief prosecutor for war crimes in the former Yugoslavia, Carla Del Ponte, said there had been "credible" reports about the fate of Serbian soldiers held there.

Del Ponte said her investigation was shelved because of lack of evidence and resistance from senior UN figures.

However, the Guardian has obtained the report of a UN forensic examination of the Katuci house, commissioned by Del Ponte. The report, by a UN expert, José Pablo Baraybar, was previously believed to be missing. Though not conclusive, it mapped traces of blood that could have been human in two downstairs rooms. Discarded in a nearby stream, the report said, was material "consistent with surgical overalls", syringes, a handgun holster, pill containers and bottles, and four empty drug containers, including one that contained a muscle relaxant.

Asked about the traces of blood found by the UN forensic team, Katuci said it originated from when his wife gave birth. The discarded medical equipment, he added, was used by his family to self-administer drugs because the nearest hospital is several hours' walk away.

But Baraybar, the former director of the UN's missing persons and forensics unit in Kosovo, said his team found "highly indicative evidence" that pointed to organ removal at the Burrel house, and prosecutors received testimony from eight witnesses.

They comprised "foot soldiers" who claimed to be present during the surgery, he said, and a driver who claimed he brought small groups of Serb soldiers to the house from across the Kosovo border. The driver then described taking conspicuous packages to Tirana airport, bound for flights to Turkey. The surgeon conducting the operations was identified as a Kosovan doctor from Pec, Baraybar said.

'Slaughterhouse'

"What the sources indicated was it was almost like a slaughterhouse," Baraybar said. "People came in alive, then things happened inside the house, and the people ended up dead. But certainly they were not just killed. The reference was of organs of some kind being taken out."

Angry villagers prevented Baraybar and his team from conducting exhumations at a nearby cemetery where the bodies are said to have been buried. At the Katuci house - where Del Ponte is known as "the witch" - the family of subsistence farmers show letters requesting compensation for the UN investigation, which they complained was intrusive. "They wanted to get under the floor with pick axes," said Katuci. "What I want is for light to be shed on this case so my family's innocence can be recognised."

Marty's investigation could gain additional impetus from the recent discovery of an illegal organ transplant clinic in neighbouring Kosovo. Police there raided a clinic in the suburbs of Pristina three weeks ago, arresting two doctors and the country's acting permanent secretary at the ministry of health, Ilir Rexhaj. Interpol is helping to search for a third doctor, Yusuf Ercin Sonmez, a notorious Turkish surgeon who they believe was behind the operation.

The investigation was opened after a 23-year-old Turkish man was found at Pristina airport with scars from an operation to remove his kidney.

At the clinic police found a 74-year-old Israeli man who had just received a kidney transplant. Although there is no evidence any of the individuals connected with the Pristina clinic worked in Albania, Marty is now expected to travel to Kosovo amid claims that the two cases could be linked.

Serbian war crimes prosecutors, who were denied access to the Katuci home last month, said they handed over evidence about organ trafficking networks in Kosovo to Marty's investigation.

Speaking at the weekend for the first time about his organ harvesting investigation, Marty said: "I have started gathering data from all quarters for my inquiry, and hope to visit Belgrade, Pristina and Tirana soon for further leads, including information from the Serbian prosecutor's office."

Baraybar said information gleaned from the Pristina clinic could be crucial. "If police have cracked a network of organ harvesting linking Kosovan Albanian doctors with individuals in Turkey, that is a potentially huge development for solving the Burrel mystery," he said.

For Marty, though, the focus is likely to remain on the Katuci house, where there are no obvious signs of the alleged horror story. Young children chase chickens around the same yard where, according to Del Ponte, Kosovo Liberation Army guerrillas herded their prisoners. The shed where Serb soldiers were allegedly held captive is now filled with cows. Thick Albanian coffee simmers on a stove in the room where Baraybar discovered blood stains.

"Do we look like a family that would do this stuff?" said Katuci's nephew, Defrim Kadiu, 32.

"Does this house look as if it's been treated as a hospital for 300 people? If it's true, then my family needs to be hanged in front of everyone."

Backstory

Of all the many atrocities that human rights groups want investigated from the 1998-99 Kosovo conflict, the alleged harvesting of organs from Serbian soldiers by ethnic Albanians is one of the most gruesome. Hundreds of Serbian families have for a decade been demanding what happened to those who disappeared during and after the war. In April, Carla Del Ponte the former UN war crimes prosecutor, gave greater credence to suggestions of a macabre operation, in which as many as 300 Serbs were allegedly abducted and transported to Albania to have their organs removed. In a memoir, she wrote: "Victims deprived of only their first kidney were sewn up and confined again inside the shack until they were killed for their vital organs."